A nonlinear system is a mathematical or physical model that does not satisfy the property of linearity. In other words, it means that the behavior of such a system cannot be accurately described by a straight line when plotted on a graph. Nonlinear systems are more complex and can exhibit various types of behaviors like chaos, bifurcation or hysteresis. They arise in many fields including engineering, physics, economics, biology, and social sciences. Examples include the behavior of certain materials under stress, population dynamics, weather patterns, and electronic circuits. Understanding nonlinear systems is crucial for predicting their behavior and designing control strategies to manage them effectively.